An assembling process of a semiconductor device, such as an IC or the like, comprises the steps of: cutting and separating (dicing) a semiconductor wafer and the like into respective chips, after patterning; mounting the chips on a substrate or the like; and sealing them with a resin or the like.
In the dicing step, a semiconductor wafer is adhered, and thus fixed, to a wafer-processing tape in advance, and then it is diced into the shape of chip. In the subsequent mounting step, the diced chip, having a removable adhesive or adhesion agent that is contained in a removable adhesive or adhesion layer separable from the base film, is peeled off (picked up) from the base film, and then fixed, for example, to a substrate by the removable adhesive or adhesion agent for adhering and fixing, which agent has adhered to the chip.
As the wafer-processing tape for use for the above purpose, use may be made of a tape having a removable adhesive layer and an adhesive layer laminated on a base film; a tape having an adhesive layer that also functions as a removable adhesive layer, i.e. a removable adhesive or adhesion agent layer, which layer is laminated on a base film, or the like. The removable adhesive layers that can be used for the above purposes include a usual pressure-sensitive adhesive-type, and a tape having a reduced adhesive or adhesion strength when it is hardened or cured by radiation, such as ultraviolet (UV) rays, electronic rays, and the like. Both of these types are required to have sufficient adhesive or adhesion strength so that the wafer is not peeled off from tape upon dicing, and they are also required to have peeling capability to be easily peeled off upon picking up.
Further, in the mounting step, sufficient adhesive force is required among the chips or between the chip(s) and the substrate. There are proposed a variety of wafer-processing tapes.
The wafer-processing tape that can be used in the steps above basically has an adhesive agent, a base film, and a separator; and, the adhesive strength (adhesive force) between the adhesive layer (or a removable adhesive or adhesion layer) and a removable adhesive layer (or the base film in the case of the above removable adhesive or adhesion layer) is usually designed to be extremely low, for the purpose of decreasing pickup errors in the pickup step above; and, the peeling force of the above layers is designed to be quite low enough for them to be easily peeled off. Further, the wafer-processing tape should be used by being adhered to the ring frame, during dicing; and, the tape should be peeled off from the ring frame, along with the adhesive agent (or the removable adhesive or adhesion agent), such that no adhesive is left thereon after use. However, the adhesive agent layer (or the removable adhesive or adhesion agent layer) is easily separated or peeled off from the removable adhesive agent layer (or the base film) by weak force, leaving the adhesive agent (or the removable adhesive or adhesion agent) adhered to the ring frame, i.e. adhesive residue.
As a result, in the wafer-processing tapes that can be used in such an application, the portion in contact with the ring frame demands special processing, such as alteration of the adhesive agent (or the removable adhesive or adhesion agent) or alteration of surface-modification conditions of the base film, and/or special tape structure, leading to technical complexity and consequently increased production cost.
To alter the adhesive agent (or the removable adhesive or adhesion agent) in the portion for the ring frame, it is necessary to laminate a tape accurately at a particular position after punching the portion for the ring frame out from the other portion.
Alternatively, it is proposed to eliminate the adhesive residue, by changing the peeling force between the adhesive layer (or the removable adhesive or adhesion layer) and the removable adhesive layer (or the base film) in the portion for the ring frame. The peeling force means the force required to peel the respective layers apart. Methods to control the surface energy of base film include modifying the surface by high-energy radiation, such as corona treatment, and providing a primer treatment on the film surface. Although the corona treatment is generally applicable to a wide variety of films independent of the kind of the base film, the boundary of the treated portion is not distinct, and thus, it is difficult to distinctly distinguish untreated and treated portions processed only by corona treatment.
On the other hand, in the primer treatment, it is necessary to select a suitable primer material according to the material of the base film to be used, and when a polyolefin-series film is used, it is generally difficult to keep the adhesive strength between the base film and the primer on a high level, often resulting in peeling-off between the primer layer and the base film when the wafer-processing tape is removed from the ring frame, and hence occurrence of adhesive residue on the ring frame.
To control the peeling force of the removable adhesive layer, it is necessary, for example, an additional step of altering the removable adhesive to be used, making the process very complicated.
Other and further features and advantages of the invention will appear more fully from the following description, taken in connection with the accompanying drawings.